A small GTPase named ADP Ribosylation Factor 1 (ARG1) regulates the Golgi coat proteins (COPs) in order to regulate intracellular transport through the Golgi complex. Locking ARF1 in its GDP-bound form disassembles the Golgi complex and causes secretion arrest. This phenotype is replicated by the overexpression of an intracellular receptor, ER Retention Defective complementation group 2 (ERD2). We now find that overexpressed ERD2 associates with the ARF1- GTPase Activating Protein (GAP). This association does not occur normally when ERD2 is unable to perturb Golgi traffic. The overexpression of the ARF1-gAP perturbs Golgi traffic similar to the overexpression of ERD2. Thus, a stable complex of ERD2 and ARF1- GAP may mediate the perturbation of Golgi traffic. To test this hypothesis, we will generate ERD2 mutants and assess whether their ability to perturb Golgi traffic correlates with their stable association with the ARF1-GAP. In addition, mutants of ARF1-GAP that no longer has GAP activity, but can still bind ERD2, will be assessed for their ability to block the actions of ERD2 in a dominant negative fashion. Next, we will examine whether overexpressed ERD2 recruits more ARF1-GAP onto membranes to form a stable complex and whether other proteins exist in the stable complex that modulate the intrinsic activity of the ARF1-GAP. Finally, we will delineate the potential mechanistic pathways mediating the actions of ERD2 by assessing whether overexpressed ERD2 inhibits the ARF1-Guanine Nucleotide Exchange Factor (GEF) or can affect the COPs through an ARF1-Guanine Nucleotide Exchange Factor (GEF) or can affect the COPs through an ARF1- independent mechanism. Since the regulation of protein function can be accomplished by regulating its localization, an understanding of how ERD2 regulates Golgi traffic may contribute to a generalized understanding of how secretory proteins are affected by processes that regulate intracellular transport. This elucidation will contribute to unraveling mechanisms that underlie immune regulation, cancer biology, and genetic storage diseases.